Initramfs scripts for ZoL.

Since both the Debian GNU/Linux and Ubuntu packages contain these, and they're actually needed to improve (and/or create an initrd with) ZoL, including these in the main ZoL repository makes sense.

These come directly from the pkg-zfs:master/debian/wheezy/0.6.2-8_wheezy branch.

Currently no logic to put them in place is added. Manually put them in /usr/share/initramfs-tools/ or /etc/initramfs-tools/.